Tag: The History of the Universe

A million years is quite a slice of time, but imagine 13,800 of them. That’s 13.8 billion and that’s when your life story actually begins.

Perhaps the greatest understatement, serenely floating around in the vastness of the universe is the term “Big Bang”. Nothing comes close to describing what happened in that first second, not atomic weapons, not exploding stars, not even supernovae.

And, if we cherish our understatements a little longer, it was hot. Not hot like anything that could be formed on a planet, not hot like the sun which by comparison is like standing next to the air conditioning on a coolish day, but really, really hot. So hot that nothing existed, not even sub-atomic particles and everything that was to come, the stars, the planets, the universe itself was packed into a space so small, by normal definition it did not even exist. It was energy, finite, but by our standards, may as well be infinite energy.

And Energy equals Mass as Albert informed us, E=MC2 which means Energy is same as multiplying Mass (called ‘weight’ here on earth) by the Speed of light by the Speed of light (ie, squared). This means that although there was ‘nothing’ there was also ‘everything’ at the same time.

What triggered the blast, the release of that energy, may not be fully established yet, we have some competing hypotheses to work with, however it is fairly certain science will eventually create methods for testing, so we settle the matter.

What we do know is that is happened and what happened in the time slot just after the “pop” is interesting but a bit hard to comprehend. Like everything else on the subject, the time slot is impossibly short, a Planck, a fraction of a second but only much smaller, a billion, billionth etc.) it was too hot to have nuclear forces or even gravity.Max Planck with Albert Einstein

(That’s 0.000,000,000,000,000,000,000,000,000,000,001th of a second if you’re interested).

Now we all “know” that nothing travels faster than the speed of light, but during this briefest of periods before the second Planck, we had space inflation which did just that. It was so fast, the forces blasted out were moved apart more by the expanding space than by the explosion and none of that fits with what scientists already know. So far.

Then we had some cooling down to temperatures that are still so hot they are way beyond our comprehension and things like gravity, nuclear forces and electromagnetism were separated into individual forces in their own right. (To be a little more accurate, the first one out of the blocks was the weak nuclear force which broke loose in the 4 zeros between the 36th and the 32nd part of the first second when the inflation ended.)

Particles popped into existence by the collisions of energy particles (which have no mass or “weight”) into bosons which converted the energy into a particle which actually has mass. There was no ‘something from nothing’ at least from the point where the ‘bang’ occurred as there was definitely a lot of energy (another understatement) so by default there was mass, a lot of it, as they are the same thing.

From 20 seconds to 380,000,000 years (that’s 380 million years) may seem a bit of a jump to us with our mini time scales but for the universe it wasn’t even late morning when the hydrogen ions and the helium ions begin to capture electrons to become stable, electrically charged neutral atoms. Solid matter at last.

In the open reaches of space, vast clouds of stable atoms of helium and hydrogen would later coalesce under gravity to ignite the stars, but for now, some were joining forces to create organic molecules making interesting things like ice, but really, something more exciting is overdue.

600 million years later, gravity has pulled massive amounts of hydrogen and helium together. The first nuclear fires, stars form.

The very first galaxy was not large as it only takes about 300 years for the light from the outside stars to reach the middle of the pack.

That galaxy could be MACS0647-JD. It’s not a very glamorous name for what may be the first galaxy, but that’s what we have called the light picked up by one of the Hubble Telescope’s programs called the Cluster Lensing and Supernova survey. The scientists had chosen a “quiet spot” to look, somewhere southwest of Orion. It is hardly sufficient to say it is long way from here because the light from this galaxy has been scooting along at 186,000 miles per second for 13,300,000,000 years and only just arrived this morning.

Ok, so we accept the first one is a long way from here, but there are at least 10,000 others out there too in the same outer region and each one had their own billion stars (had, as they have almost certainly expired already).

The probing of this particular part of the universe is an extremely small window, an area equal to about one tenth of the night sky obscured by the moon. In between us and the long distant galaxy, new galaxies are still being formed so the universe is a pretty dynamic place these days.

To collect all that light from even a small part of the night sky takes time. You can’t just take a shot with your digital camera and head off to the pub. The instruments are set for lengthy periods of exposure with multiple readings collated via complex computer computations for the right result. To get the same level of detail for the whole night sky, the photography session would need to last a million years, give or take so we may have to settle for just this one spot for now.

Massive volumes of hydrogen and helium atoms were attracted to each other by gravity, by far the weakest of the 4 forces of nature. But because the strength of gravity is governed by the mass of the objects, qualified by how close they are to each other, gravity can become somewhat pressing.

(Actually, gravity always wins because despite being the weakest force, well behind the nuclear forces and electromagnetism, it acts long-range. Eventually objects become bigger, making gravity stronger as the mass increases.)

In this case, as the atoms bumped into each other they gradually became bound together in an ever increasing mass. The strength increased with each additional atom until the new additions were pressing down on the earlier atoms with so much force, the temperature soared something approaching 15 million of degrees.

When the temperature reached the critical point, the whole lot erupted in a nuclear fire that we call a star. Fortunately, the star does not explode in the normal sense or even “burn” in the normal sense as there is no appreciable oxygen to facilitate combustion.

As it happens, the temperature is so high, the pressure so great that hydrogen atoms begin to fuse releasing helium and energy. Strangely, the level of energy produced by a star is fairly low when measured as a percentage of its mass, but it has a lot of mass. As a result we get a very bright spot in the sky which releases a lot of energy and in the case of the earth, that is a good thing.

Fortunately the action in the core is counter-balanced by the gravity pull on the outer two thirds, so we end up with a stable firework that will persist for about 8 billion years. Our star is about half way through and while the temperature its core is 15 million degrees, where the fusion is taking place, out on the “surface” it’s a very much milder 5800 degrees, very much less than 1% of the core temperature and, perversely, less than the temperature in the corona, way above the surface at the edge of Sun’s ‘atmosphere’.

By 13 billion years ago, the first stars are clumped into the first galaxies which is essentially, a whole lot of stars clumped together, but in terms of distance, “clumped together” hardly gives an accurate impression of the size of a galaxy.

Take our own galaxy The Milky Way as an example. Our Sun is just one of 200,000 million similar stars but to get from one side of the galaxy to the other, will you’d need to pack a big lunch.

Technically, it may be possible to build a craft that could travel close to the speed of light. It would have to be very large to accommodate enough fuel to burn constantly for several years, but eventually it could reach speeds approaching 186,000 miles per second. At this speed you could get to the middle (once you decide where exactly that is) in about 20,000 or maybe 30,000 years. If you went the other way, to visit another galaxy, well, they are rather a long way from each other so there’s probably not much chance of visiting another galaxy anytime soon.

In Universal terms however, galaxies are not that far apart and they tend to be in clusters too, anywhere from a couple of dozen to a several thousand. Virgo for example is a super-cluster and has something approaching 2,500 galaxies. Three of these galaxies are really giant ellipticals and each one is around a million light years across. Compare that against our own humble spiral’s 100,000 light years across. We’re actually in a relatively isolated group of only 50 galaxies including the Andromeda, which we will get to shortly.

We shouldn’t assume that seen one galaxy you’ve seen them all. Our home galaxy is the spiral type full of extra gas and dust with long arms in which new stars are being formed continuously. Other types have practically no gas clouds and have different shapes too, including lenticular, elliptical galaxies and irregular galaxies like the dwarf Sagittarius galaxy currently being ”eaten” by the Milky Way. (It rotates through us at a right angle to the disc and every time it passes through, more stars are ripped off to become part of the Milky Way.)

Some of the small galaxies can have a mere 10 million stars. Ten million like our Sun. Imagine having a dollar for every million stars. If you owned a small one, you’d only have $10 but if you owned the Milky Way, you’d have $200,000. Now if you owned a really big galaxy, well the larger ones have up to 10 trillion stars Of course you would have to be careful how you treated the super black hole in the middle.

When galaxies meet, as ours will when it runs into Andromeda, at a leisurely 500 kilometres a second, there is little chance of stars directly colliding because of the space between t hem, but gravity will severely distort the shape of the combined mass. After they pass through each other and throw out a few unfortunate stars into intergalactic space, they will slow down, essentially stop and start moving back towards each other again for another collision. Eventually they will become one. Of course, we will not be around to witness the best bits as the process takes somewhere between a couple of hundred million years and a really long time.

12 billion years ago, after an unimaginable time span of 1,800 million years since the Big Bang, stars in this area ignite forming the Milky Way, our home galaxy

It’s somehow comforting to think we have neighbours, perhaps lots of them, in our locality. Our galaxy is a spiral, that is, a centre disc with 4 major arms and fairly big as galaxies go, nothing like the real big ones but not a tiddler either at 120,000 light years across.

If our Sun and Solar System was the size of a coin the Milky Way would be about the size of China or the US.

If you thought of it as a very big city 120 kilometres across, our suburb (which in addition to the Sun has another half a billion other stars probably all with their own solar system) is 27 kilometres out of town on the Orion–Cygnus arm. All up, as far as we know, there are between 200 and 400 million stars here, but you can’t just count them and on average, it produces one new star every year although that many probably close up shop too.

The main problem is that not only are we a fair way out of town, on one of the big avenues, there are three others just as big. (Actually we are not right on the avenue, more like a side street off one of the main avenues.) To put that into perspective, if our Sun and Solar System was one inch disk (25mm) the Milky Way would be about the size of China or the US.

When you think that our solar system has 8 planets made up from the leftovers from the sun’s birth, it’s hard to imagine all those other suns out there don’t also have at least a handful of planets too. To add to the fun, recent data from the Kepler space mission points to planets that are not attached to stars, just wandering about, probably a couple of hundred million of them.

Getting back to planets doing the right thing, the data strongly suggest that there are up to 40,000,000,000 planets orbiting stars in the habitable zones and 11,000,000,000 of those look just like our Sun. This is just in our galaxy so all that adds up to a lot of neighbours, but don’t expect a visit tomorrow. The nearest star to us (other than the Sun obviously) would take more than four years to get to and that’s only if we can work out some way to travel at the speed of light and we don’t bump into a speck of dust or something a little larger. The closest one that might have an earth-type planet is 12 light years away.

The reason the neighbourhood has a milky look about it is that our vision has only evolved to help us find things to eat and avoid others that might want us for lunch. Our eyes did not evolve to see stars, which is why we can only see about 10,000 of them (all in the Milky Way, although some argue Omega Centauri is just outside our galaxy) meaning we can see one star in 40,000. (An exception is the temporary super-bright flash of the death of a star, a supernova). The light from the rest blends into the band of light we see on dark nights. The dark patches are caused by interstellar dust that masks the light from the stars.

It must have come as quite a surprise to Galileo, to see so many stars when he put his telescope up to his Mark-1 eyeball in the year 1610. He was the guy who worked out the earth was not the centre of anything and got belted up by the Catholic Church for saying so. All the way up to the 1920’s scientists thought the Milky Way was the only show in town.

Man, were they wrong, and by a margin that’s impossible to grasp. There are literally billions of other galaxies out there (170 billion to put a figure on it) most of them holding billions of suns and you can’t even see one star with the naked eye, only a few distant galaxies of stars.

By 11 billion years ago, the first stars in the Milky Way were 1,000 million years old and by 10 billion years ago, the galaxy had taken on its spiral shape, continuously creating new stars. It’s sobering to think that at this stage our Sun is still 5.4 billion years in the future.

At the 9.5 billion year mark, while some new stars are forming, some are already collapsed after burning up their hydrogen, but at this point, there are no planets yet. Half a billion years later and dying stars, red giants like the future for our Sun, fuse hydrogen into atoms of the 26 lightest elements, lithium, carbon, oxygen through to iron. Atoms of iron were now abundant in space.

At the 8.5 billion year mark, the big boys were making their mark, Supernovas, the death of massive stars, explode and form large quantities of the 60 heavy elements including silver, gold and uranium. Vast amounts of these elements combine with iron to form rocky planets which now orbit close to new stars. Further out gas giants, too small to become stars, orbit.

Despite production of massive amounts of other elements, hydrogen and helium still make up 98% of reflective matter and now, at 6 billion years, the universe is already twice as old as planet earth will be, when it is born in another 1,360 million years forward of this time.

At 5 billion years ago, after more than 8 billion years have passed, a cloud of dust, gas and debris coalesce into a massive hot object in this outer region of our galaxy. A mere 400,000 years later, light emerges from the cloud and our Sun is born, and with it, a little planet we call home.

There are about 300 ‘Days’ of Earth History, listed in our ‘Diary of The Universe’ poster and it’s interesting to follow the development of our little patch. You can download the whole poster for printing.